Automatic telephone system



J. ERICKSON.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATxoN man 050.30, 1904.

1,354,605. Patented ot. 5,1920.

- l/ mh lli[lllllllllllllHlly J. ERICKSON.

AUToMAnc TELEPHONE SYSTEM.

APPLICATION FILED DEC. 30,1904.

1,354,605.v Patented 001151920.

' 3 SHEETS-SHEET 2.

.T-METTI' J. ERICKSON.

AUOMATIC TELEPHONE SYSTEM.

APPLICATION FILED DEC. 30, I9o4.

1,354,605. rammed oat. 5,1920.

3 SHEEISWSHEET 3.

m- UUEUZU citizen of the United States of America ,UNITED STATES PATENT OFFICE.

JOHN ERICKSON, 0F CHICAGO, ILLINOIS, ASSIGNOR, `BY MES-NE ASSIGNMENTS, TO AUTOMATIC ELECTRIC COMPANY, A CORPORATION OF ILLINOIS.

AUTOMATIC TELE' li:

Specification of Letters Patent. Y

Patented Oct. 5, 1920.

To all whom t may concern.'

Be it known that I, JOHN Enronson, a

3 and resident of Chicago, Cook county, Illinois, have invented a certain new and use' ful Improvement in Automatic Telephone Systems, of whichthe following Vis a specilication.

My invention relates more particularly to that well-known type of automatic telephone system in which each subscribers line is provided, at the centralstation or other suitable place, with a so-called first selector-switch, and in which there are also a suitable number ofso-called connectorswitches,'each first selector being individual to a subseribers station, and employed by the subscriber, when calling la number, for automatically selecting an idle trunk-line, and the said connectorswitches being preferably less in number than the subscribers stations that is to say, each connector-switch being common to a number of subscribers7 lines, and employed, after the proper trunk-line connection has been established through the medium ofthe selector-switch, for mak` ing the final connection with the line of the called subscriber. A My invention has special reference to an automatic telephone system of the fore going general character in which the socallec vertical7 and rotary relays of the said first selector-switches, or other individual switches, are normally bridged across the subscribers lines'.

Generally stated, the object of my vention is to provide means for automatically cutting off, or opening up. theV bridge containing said relays, or other electromagnets, of the called subscribers line, when a connection between such line and the line of the; calling snbscriberis finally established, so as to prevent short circuiting of the voice-currents through the said bridge while the subscribers are talking, and, among other things, to prevent the said relays from chattering and'from being operated when the ringing current is thrown onto the line for the purposerof ringing the -bell at the called subscribers station.

A special object is'to provide a construction and arrangement whereby each first 'selector-switch or other suitable individcut-off relay, and whereby the said bridge cut-off relays may, in each case, be energized by the flow of current through a circuit which is closed as soon as the connector-switch establishes connection with the called subscribers line.

x It is also an object to provide certain details and features of construction tending to increase the general efficiency and serviceability of abridge eut-off arrange-v ment of this particular character.

To the foregoing and other useful ends, my invention consists in matters hereinafter set` forth and claimed.

Figure l of the accompanying drawing is a diagram illustrating, in as simple a manner as possible, an automatic telephone system embodying the principles. of my invention.

Figs. 2 and 3 when taken together represent a complete connection from a calling to a called telephone line through a first selector., second selector, third selector and connector of the type of system which was installed in Los'Angeles, California. These figures show the details of the circuit arrangements completely and are the basis for the schematic diagram shown in Fig. l.

As thus illustrated, the two subscribers stations A and B are shown with their lines fully connected up through the medium of a trunk-line and a first selector and a connector switch. The first selectorswitch of the line leading to the subscribers station A is represented by the socalled vertical and rotary relays D and E, and also by the bridge cut-offI relay F. Other familiar elements of the said first selector-switch consist of the side-switch G and the vertical and rotary wipers H and I. The so-called normal post arm l will also be recognized as. a part of a wellknown construction of first selectorswitch.

The connector-switch is represented by the usual vertical and rotary relays K and L which are bridged across the trunkline conductors M and M1; and the bridged back-release relays N, which are a part of the said connector-switch, arealso shown. The private wiper O of the so-called sideswitch of the connector-switch is also illustrated. And the verticah private and rotary wipers of the rotary shaft of the said connectonswitch are indica-ted at -subscriber"s tirst selector vide an arrangement whereby this bridge will also be opened when the first 'selectorswitch77 remains unopera'ted. In other words, I provide an arrangement whereby the calling subscriber may, in addition to opening the bridge ot his own ,selector also opens the bridge el3 the called subscriber. selecton Y illith an arrangement or the roregoing character, it is obvious that the calling sub- -chised contacts o, energizing the relay V also sepa y'ares the third contact el from the other two. rllhis, it will be seen, not only produces a break in the bridge between the two relay-coils, but also disconnects both coils from the battery Z1. it the leift of the diagram,jthe three contacts 29, 30 and 3l all remain in Contact with each other; but although this leaves the battery connected with the coils oi" the relays E and D, it will be seen that nothing undesirable results therefrom, owing to the tact that the side switch G has beenope y'ated in such manner as to disconnect both relays Yfrom the line circuit. i

It will be understood that the wires, 7, 8 and 9 lead, respectively, to the rotary vertical and private bank-contacts oi one or more connector-switches.

By cutting off or opening up brid' across Vthe called subscribers line therer then no danger of the called subscribers individual switch, such, for example, as the rst selector shown, being operated when signaling current is transmitted to the called substation. In a bridging system, and with the bridge lett across the called line, the signaling of the called subscriber would be liable to energize the relays of the called or other individual switch. and thus operate the same to an ott-normal position. Should the called subscriber afterward attempt to malre call he would not obtain connection with the desired line, or would evperiencev other trouble. In other words, the transmission of the signaling current over the called line would cause the called subscribers individual switch to a trunlr line, which trunk line would be uselesslyflered busy during conversation between he twf.; subscribers. All this trouble is avoided by the use ot my bridging` system involving means for cutting oli or opening up bridges.

Following is a description of the telephone system as installed in Los Angeles, California, and which given here as a basis to the schematic diagram oit TEig. l, and in order to enable any one slrilled in the art to produce a system such as shown in lig. l having in mind the details of the various mechanisms and circuits as hereinafter set forth.

The system shown in Figs. 2 and 3 consists of a calling telephone A', a selector E individual thereto and having access through a second selector F to a third selector Gr, (Fig. The selector G in turn has access to a connector switch H (Fig. 3) which in turn has access to called lines such as B. It will be understood that in the system a part of which I am herein describing, there were as many switches E as there were telephone lines and that there were also a plurality of switches such as F', G and I-I accessible to calling sub` scribers inv commonn I have shown only those switches necessary or use when a calling subscriber desires to extend a connection to a called subscriber and will explain the succession ot operations which talre place whenV the calling subscriber il. removes his receiver' and operates his calling device to set up a con` nection to a called subscriber B (Fig.

The subscribers substations are oi' a type well known to those skilled in the art and comprise the usual talking instruinentalities and a calling device which is adapted after being rotated by the subscriber to iii-s Vt ground the vertical line conductor lO a predetermined number or" times, and thenV to ground the rotary lineV conductor ll once. ringing key l2 is also supplied by means ot which the vertical line conducto;l connected to ground. Y

Assuming the directory number ci@ called line shown is 22220. their subscriber will tirst remove his recer the switch hook and tllei ci xilliner device in accordance with t. e various d' ot the called number. ."s rises when the Y springs 13 close to c ground post the r. front contrt t ot the ringing ilk second level ot the hanlr. it the saine time the wipers moving vertically causo the off normal springs to operate to open the circuit ot relay li" and connect ground to the private normal conductor to make the line ot suhstation Ell husy. launrdiatelj," aiter these tiro impulses are delivered to the tical line7 the tooth 2O ot the impulsi-i ufl connects ground once to the rotary line con doctor YllY thence through rota y line relay 2l and through the springs ot out oit relay lf? to battery. fiel y Qi responds to delirer one impulse Yfrom ground through sprinos, and through the private nu `het 'l to l rlhe private m Qnet operates in resi ise to this impulse to step the side switch wi pers to their second position.

ln second position a circuit is completed from ground through second position of side switch and through the rotary magnet 22 and its interruptor springs to battery. 'll he rotary magnet ojjierates once to step the lire and private wipers onto the lirst set ot contacts in the level opposite which they stand. rlhe rotary magnet also has an extension on its armature Which acts to pull up the armature olf the private magnet 15h so that, it the iirst trunlr line in this level is idle and no ground therefore present on the private contact thereot', then the side switch will immediately step to third position as the rotary magnet falls hach to nrevent further operation ot the rotary mi and to extend the connection through the line to the line Wipers.

lilowevcr, assume that t ie first trunk line is husy and ground pr sent on its private Contact, then a. circuit Will he closed -from ground through the private contact and Wiper through h.. ylr release relay 2li, side switch wiper in second positioin and through private ma gnet i8 to battery. The resist-ance of private magnet 'itl prevents the energization of relay 2li at this time hut the private magnet 18 is energized and holds its armature in its attracted position to prevent the release oit the side switch to third position. .he rotary magnet therefore will again energize as soon it falls haelt and closes its interruptor springs and Will step the Wipers to the second set oit contact-s. This hiv/Aer action of the rotary magnet will continue until an idle trunk line is reached and then magnet 1S heing no longer held energized will allowv the side switch to pass to third posit-ionj extending the connection to a selector such as F. rlhe side switch Wiper in passi. V1 to third position connects ground through relay Q41: to thc Wiper and thence the privato con tact and its multiples of the connected with switch ll to 'prevent another switch E from seizing the same.

Les/,noos

The suhscriher Will now again operate his callingdevice vtor the second digit 2 and will in this case control the -vertical and rota-ry line relays 26 and 2T ot the second selector ll". rthe line relays ot the selector ll Were cut ott :from the line circuit the movement of the side switch to third position.

The relays 26 and 27 are controlled in the same manner as were the relays of selector lil to irst step the Wipers vertically hy means ot the vertical magnet 28, to then operato privato magnet 29 to step the sizl switch to second position, after which the rotary magnet 30 and priif'ate magnet 29 cooperate to rotate the Wipers until an idle trunk linel is found, after Which the side switch passes to third position to connect ground through hack release relay 3l to the private contact ot the seized trunk and to cut oil the line relays et the switca F and extend the connection through the line Wipers to thc lino relays 82 and ot the sei ed switch Gr. y crated the oil normal springs close to light the lamp to indicate to the attendant that the switch is in use.

The next operation of the calling device in response to the third digit Q causes the operation of the line relays 32 and 33' in the same manner as tor preceding switches. .Relay 82 operating the vertical magnet Sil to step the Wipers to the second level and relay operating the private magnet 35 to step the side switch Wipers to second position to start the operation oi the rotary magnet 3G. This switch G has one additional side sWitch Wiper 37 Which operates to disconnect the vertical magnet in second and third positions to prevent its 'further operations hy the line relays which in this switch remain permanently bridged across the trunk circuit and are not cut oil as in the preceding switches. rlfhe rotary magnet 36 operates to rotate the wipers to the iirst idle trunlr line atter which the private magnet permits the side switch to pass to third position, extending the connection through the line Wipers to the connector switch l-l and connecting ground direct to the private Wiper 8S through the side switch vWiper 39.

This operation ot the calling device 'for the 'fourth 'digit FZ iirst causes tivo cnergizations of the vertical line relay 39 which in turn twice energizes the Vertical magnet Lll over a circuit from ground through springs d2 and 43, main spring` and hack contact ot private magnet dei, side switch 'Wiper i5 in first positiom and through vertical magnet all to battery. The following rotary impulse operates relay 40 which closes springs 46 and springs and 4l?. rlhe closure ot springsl is Without effect at this time hut the closure of springs i3 and il? causes the operation of prit/ate magnet ltto step the side switch wipers to second position. Wiper 45 in second position prepares a circuit for the rotary magnet 48, substituting it for the vertical magnet in the circuit controlled by the vertical line relay The side switch wiper 49 in second position prepares a circuit tor the release magnet 50 which will be explained.

N ow as the calling device is operated for the last `digit naught, the line relay 39 again operates in response thereto and in 4this, case Atransmits corresponding number of impulsesA through the rotary magnet 48 through springs and 43 to step the wipers onto the set of contacts in the level elected to which the called station B is connected. ritter this the rotary line relay 40 will again be operated by the final rotary impulse and will again close springs 46 and springs 43 and 47. `The private magnet will again energize. ln case the called line should be found busy either from calling or being called, then ground will be present on private contact 51 either from the off normal springs of the called subscribers individual switch C or from the wipers of some other occupying switch (not shown). ln either case, the private wiper 52 being connected with contact il, then when the relay 40 engizes as pointed out and springs 46 close, circuit will be completed from ground, contact 5l, wiper 52, side switch wiper 49 in second position.y springs 45, and through the release magnet 59A to battery. The magnet 5l) inlined itely releases all the mechanism of the connector H and itis restored to its s rnial position with its oli normal springs 53 open and its sine switch in first or normal position. Illhe calling subscriber Anow havi' j completed the calling operations presses c ringing key lQat the substation. lnstead ot performing any ringing operation, however, the impulse ot ground through the urging lrey operates re ay 89 which in turn operates the vertical magnet one step and thereby closes the ott normal springs 53 to ect the lead. trom the busy signaling machine 54 to the vertical line conductor. rThe calling subscriber upon hearing the busy tone .'ill hang up his receiver and release the connection in a manner to be pointed out.

Assuming however, that the called line is vidle when connection vis made therewith, then no circuit will be closed for the release magnet when relay 40 operates, and the private magnet will permit the side switch wipers to pass to third position. rlhe wiper The wiper 49 in Relay. 55

energizes to disconnect the vertical and rotary line relays ot the called line therefrom to prevent any operation ot tie switch C when the called subscriber answers. Other side switch wipers of the switch'll passing to third position extend the connection to the called line through the lino wipers and springs of the ringing relay 54. lChe calling subscriber will now press` the ringing key l2 to operate the line relay 39 vot the connector which in turn operates the ringing relayV to disconnect the -called line trom the calling line and to connect the ringing generator to the called line to operate the ringer thereof. The called subscriber will remove his receiver and conve 'se'fu ith the calling subscriber in response to this signal.

The release ol the connection after conversation is laccomplished as Vfollows: Should the calling subscriber be the lirst to restore his receiver, then springs 14, l5 and 16 will be brought into contact to connect ground to both vertical and rotary line conductors simultaneously. This grounding ot' both line conductors will energize the line relays 32 and 33 ot the third selector and the relaysv 39 and 40 of the connector simultaneously with the results following: Relay 40 will energize the private magnet 44 over a circuit previously traced and relay 39 will theretore complete a circuit troni ground through springs 42 and 43, main spring and front contact ot the private magnet, and throughV the release magnet 5() to battery. Magnet 50 returns the switch H to normal. lielays '32 and in a similar manner close the circuit for the release magnet 56 olf the switch Gr which releases the switch il and in turn closes a back release circuit for the preceding selector F 'from battery through resistance 57, springs 5S, private wiper and contact of switch F, and through the baclr release relay 31 to ground at the third position ot' the side switch. Relay 3l closes a circuit tor the release magnet 59 ot switch l1" to release said switch and this magnet in turncloses similar circuit tor the back release relay 24 of the individual selector E Tdelay 24 in turn closes the circuit of the release magnet 60 of the switch t thus restoring the entire connection to normal. f

ln case the called subscriber is the first to hang up his receiver then the release ot the first, second, and third selectors is the same as above described when the calling siiibscriber .hangs up, but Vthe connector is released by the hanging up of the called party as follows: The downward more ment ot' the called subscribers switch hook closes the release springs 61, 62 and 63 in contact, thereby grounding the called sul scribers line conductors simultaneously to energize the two back release relays 64 and 65 or" the switch H. Relays 64 and G5 conjointly close a circuit tor the release inagnet 50 of the connector 'from ground through the three springs controlled thereby and over conductor 6G through the magnet 5i) to battery. Magnet 50 releases the connector H to normal. lt will be understood that, should .the calling subscriber have desired to release belfore the call had progressed to the third selector F then the release would be controlled by the operation ot the last switch in the connection, either ll or F in the same manner as lperioriiied by line relays of the switch G.

1vVhat l claim as my invention is l. rin .automatic telephone system comprising iirst selector-switches which are individual to the subscribers, and which are each provided with normally bridged relays, and also with a bridge cut-oill relay for opening the bridgein which the said relays are included when the subscriber to whom the switch is allotted is called.

2. in automatic telephone system comprising subscribers7 lines, a iii-st selectorswitchl for each line, and a suitable number ot "connector-switches, together with means i'ior supplying current for the operation of said switches, each selectorswitch being provided with a pair ot relays normally bridged across the subscribers line to which the switch is allotted, and also with a bridge eut-oil relay adapted to destroy the continuity of the bridge in which the relays are included when the subscriber to whom the switch is allotted is called, each bridge cut-oit' relay having a normally open circuit controlled by one or more et said connectorswitches.

3. ln an automatic telephone system, the combination oi subscribers lines, a selecton switch for each line, each selectoi-swi.tcli having an electro-magnetic device normally bric 'ed across the line, and a suitable numi ber of lconneeter-switches", each selectorswitch being individual to its allotted subscribers line, but each "connector-switch being` common to a pliirzility oi" subsciibersI` lines, and each lseleetor-switch7 having a bridge cut-oil relay adapted to destroy the continuity oi the bridge in which the said el etre-magnetic device is included when the subscriber to whom the selector-switch is allotted is called, together with means tor supplying current, and with which one terminal of each bridge cut-oli' relay is permanently connected, the other terminal ot' each bridge cut-otl relay being normally connected with one or moie oit said con- Vnectoi--switclies, substantially as described and t'or the purpose set forth.

in an automatic telephone system, the combination ot a selector-switch provided with a bridge including a switch-operating element,` a bridge cut-oit relay, a battery, and a normally open circuit including said internos bridge cut-oil relay and battery, together with a lceniieetor-switch provided with a plurality ot wipers, whereof one is a socalled private wiper, the said private wiper, when the connector-switch is operated, being adapted to close the circuit ot the said bridge cut-oil relay.

5. ln an automatic telephone system, the combination of iirst selectorswitches77 which are individual to the different subscribers, and conneeter-switches which are common to the diillerent subscribers, each selector-switch being provided with an electro-magnetic device having one terminal normally connected with a switch contact or contacts ot one or more of said coniiector-switches, a source olf electric current connected with the otherterminal thereof, and an operating magnet controlled by saidV electromagnetic device.

6. ln a telephone system having a calling subscribers line, a called subscribers line, parallel circuit conductors connecting the calling subscribers line with the called subscribers line, a condenser in each circuit conductor, and means for setting up and releasing said connection including a battery having one pole grounded, the provision oi back bridge relay means bridged between the parallel conducting paths at a point between the condensers and the called line with a connection between the bach bridge and the non-grounded pole oi said battery, and a called subscribers bridged relay means together with a bridge-eut-otl relay operated by the calling subscriber to open up or cut oft the said called subscribers relay means.

7. ln a telephone system having calling and called subscribers lines, with a temporary circuit connection between the two lines including a condenser at each side ot the circuit, and having means tor setting up and releasing said connection including a pair of relays bridged across the circuit on one side oi' the condensers, the provision of another pair el relays bridged across the circuit at the other side of iid coiiiilensers, a battery having one pole grounded and its other pole connected with the middle point oil' each relay bridge, together with a relay bridge individual to the called subscribers line and another relay individual to the called siibscribei"s line and controllable by the calling' subscriber for cutting oil or opening up the said individual bridge.

8. ln a telephone exchange ein, combination of subscribers7 telephone lines.y a normally closed iiidiviilual bridge eontaining electromagnetic devices; normally across each line, an automatic switch controlled by said electromagnetic devices, and an individual relay tor each line, said relays ada ited to open said bridges when energized and close the same when denergized, each entire the.

said relays located at the terminals of theiry lines.

9. ln a telephone system, the combination of subscribers lines, an individual bridge containing .electromagnetic devices for each line, an automatic switch controlled by said electromagnetic devices, an individual relay for each line, said relays controlling the continuity of said bridges, each entire bridge being individual to its allotted line, said relays located at the terminals of their lines, and means by which a calling subscriber operates the relay of the called line.

10. In a telephone exchange system, the combination of a telephone line, a bridgeV across said line, a private normal for said line, a bridge-cut-oil-relay for said line, and a circuitfor energizing said relay when the line is called, said circuit including said private normal.

11. A telephone system comprising a suitable line, a relay for said line, an electromagnet to be maintained energized when connection is extended to the line and the said relay is not to be used, means for rendering the said relay inoperative when the said magnet is energized, and means for retaining the relay in operative relation to the line whenthe latter is used for calling in the opposite direction. Y

12. In a telephone system, a calling subscribers line, a called subscribers line, means including automatic switches controlled by `direct current for trunlring the v calling line linto connection with the caller.

line, a normally closed bridge across the called line, and means under the control of thev calling subscriber for temporarily destroying the continuity of said bridge.

13. In a telephone system having calling and called subscribers lines, with means for setting up and releasing a connection between said lines including parallel circuit conductors having a condenser in each circuit conductor said means including a bridge of said conductors and means controlled thereby having vertical and rotary motion to find the called line in a selected group, the provision of back bridge relay means bridged between the said parallel conducting paths at a point between the said condensers and the called subscribers line, a battery having one pole grounded and a connection between the back bridge and the non-grounded pole of said battery together with a called subscribers bridged relay means and a bridgecut-oilI relay operated by the calling subscriber open up or cut oli3 the bridge oi'. said called suhscribens relay means.

ln a telephone system having calling and called subscribers lines, a temporary circuit connection between the two including a condenser at each side of the circuit and means for setting up and releasing said congether nection including a pair of relays bridged across the circuit at onerside of said condensers, a pair or' relays bridged across the circuit at the other side of said condensers, and means controlled by said bridges having vertical and rotary motion to lind a called line, the provision ot a battery having one pole gro `led and its other pole connected ff l .L point each relay bridge tca relay bridge individual to the *v with called subscribers line, and another relay vindividual to the called subscribers line and controllable by the calling subscribers for cutting oil or opening' up said individual relay bridge.

15. ln a telephone system, the combination of subscribers lines, an individual bridge including a switch-operating element; for each line, means having both vertical and rotary motion to seize called lines, one motion to select a group and the other motion to {ind the called line in the elected group, an individual relay for each line, said relays controlling the continuity ci" said bridges, means for cnergizing the relay of the called line after the completion or both motions.

16. In va telephone exchange system, the combination of a telephone line, a bridge including a switch-operating element across saidline, a private normal for said line, a bridge-cut-oii relay ior said line, a circuit 'or energizing said relay when the line is called, said circuit including said private normal, and means having vertical and rotary motion to seize said line and close said circuit.

171A telephone system comprising a called'subscribens telephone line, a relay allotted to said line and controlled by the subscriber thereof, an electroma net adapted to be energized to place the said relay in inoperative relation to the called line, a circuit for continuously energizing said electrzr magnet when the line is called, and means having vertical and rotary motion under the control of the calling subscriber for closing said circuit, one motion to select groups and the other motion to find a line in the selected l group.

A telephone system comprising a sub-- scribers telephone line, a line relay tor said line, a second relay for rendering the line relay inoperative when the line is called, a connector provided with switch wipers and 1 ving vertical moti' n tcselcct groups and l, motion to connect with the cal` ff; line in any selected group, a. circuit for energizing said second relay by a flow or current through one of said wipers, and means for controlling the ope ation of the connector to extend connection to said line.

19. In a telephone system., a subscribers line, a bridge containing a switch-operating element on said line, a relay controlling the newness continuity ci said bridge, means having vertical and rotary motion r soir/ling said line, one of said motions bei g necessary :tor selecting the desired group ol lines,A and means ifor energidng said relay when the line is seizedb 20. ln a telephone system, a line, a bridge containing a switch-oper-ating element normally closed across said line, a bridge-rutoll' magnet, a connector rr vided with lino Wipers having both vertical and rotary mo tion to iind said line, and a third wiger 'lor closing a circuit through the said magnet when the line is seized.

2l. ln a telephone system, a line, a bridge containing a switrhbperating clement normally closed across sai-:l line, a bridge-cutoll magnet, a conne :tor provided. with line Wipers haring both .f'erticcl and rotary motion to iind said line, one of said motions being necessary iior selecting the desired group oi lines, and a local circuit closed through said magnet Wl en the line is seized by the connector.

QQ. ln a telephone system having a tele phone line land mea s tor signaling on said line, the provision of a bridge across said line at the exchange including a relay, an automatic switch controlled by said relay, and means responsive to 'the calling` party :tor preventing said relay from responding to the signaling current.

23. ln a telephone system in which there is a selector and a connector each having vertical and rotary motion and each provided with a bridging relay controlling the vertical and rotary motion thereof, and in which there is means for signaling on the called line alter connection has been eX- tended thereto by the selector and connector, the proifision of a switch ifor the called line operative only When the said line is used as calling line, and means 'lor preventing said switch irom operating when the called subscriber is signaled.

2l. ln a telephone system ln a called line and means 'iler extending a connection to said line and tor signaling thereover in cluding an automatic selector switch having vertical and rotary motion and a bridging relay ifor controlling the vertical and rotary motion thereof, the provision of a trunking switch 'for the called line operative only when the line is used a calling line, and means YIor preventing the said switch from operating when the called subscriber is signaled.

25. ln a telephone system in which there is a called line, means ilor extending a connection thereto and Ylier signaling on said called line, comprising an automatic connector switch having vertical and rotary motion, a bridging relay for controlling said Vertical and rotary motion, means for a telephone system, the combina- 4lrst selectors and connectors bridged the ta hing circuit; means for controlling said selectors and connectors to eX- tend connection the called line, and means :tor automatically rendering the called line inoperative ifor calling `While the connection thereto exists.

ln a telephone system, the combination oll a lirst selector bridged across theI talking' circuit and having vertical and rotary motion; means controlling said selector in accordance with the lirst digit oi the called number, said selector provided with a bridging relay controlling` the Vertical and rfiitary motion thereof, means lor ex tending a connection to a called line, and means automatically operatiif'e to render the called line inoperative lor calling While connected with said selector.

28. ln a telephone system, a iirst selector bridged across the talking circuit having vertical and rotary motion; means for controlling said selector in accordance with the first digit oi" the called nnmber, the said selector provided with a bridging relay cont-olling the Vertical and rotary motion ther: t, means ior extending connection to a ine, a bridge containing a switch-op- Y i element on thc called line, and means automatically operative to open said bridge when connection is extended to said line through the medium of said selector.

29. ln a telephone system in `which there is a called line and means for calling and Y g the called subscriber on said line, the provision of a trunliing switch indiidual to saidV called line having a bridging relay and trunks leaning therefrom said y being operative only 'when the line is used as a calling line and means 'tor preventing energizing olf said relay When the line is called and the subscriber signaled.

BO. ln a telephone system, a trunk-select4 ing switch provided with a bridge across the trunk conductors thercoil", said bridge including a sWitclroperating element, means for establishing a talking circuit through said switch, and means ilor cutting off said bridge during talking.

3l. ln an automatic telephone system, the con'ibination With a metallic telephone line oli a selector switch at the central ollice, a third conductor, a pair of control magnets and a source oi: current normally connected between the limbs of said line and said third Y maintain a severed connection between said limbs and said third conductor While the line is a Called line.

32. In an automatic telephone system, a telephone line adapted to be extended in two limbs through the central oiiice, a switch for said line, a pair of electromagnets and a source of currentI in a by-path from the limbs of said line for controlling said switch, and a cut-off relay adapted to separate said bypath from the external telephone line When said line is a called line.

33. In a telephone system, a line,'a bridge individual to said line and containing switch operating elements normally closed across said line, a bridge out-oil1 magnet, a connector provided with a pair of talking Wipers for finding said line, and a third Wiper independent of the talking Wipers for closing a circuit through said out-olf magnet when the line is seizedas a Vcalled line.

Signed by me at Chicago, Cook county, Illinois, this 30th day of November, 1904. JOHN ERICKSON. Witnesses:

W. LEE CAMPBELL, JENNiE NORBY. 

